Magnetic disk drives include at least one magnetic disk and at least one associated head slider for reading and/or writing data onto the magnetic disk. The head slider is mounted on a suspension which supports the head in a proper orientation with respect to the disk, and an actuator mechanism positions the head slider at desired radial positions or tracks of the disk.
Typically, the disk has a flat magnetic surface and is mounted on a spindle which is rotated by a spindle motor. The head slider is typically arranged to have an air bearing surface for flying the head slider closely adjacent the disk. The head slider flies on a film of air between the air bearing surface an the flat magnetic surface of the disk during rotation of the disk by the spindle motor. In order to establish the fly height of the head slider air bearing surface, the suspension typically provides a spring force against the head slider for loading the head slider against the film of air.
A typical suspension includes a load beam and a flexure. The load beam normally has an actuator mounting portion for mounting on the actuator, a loading region for mounting the flexure at the distal end of the load beam, and a spring region between the actuator mounting portion and the loading region for providing the loading force. The flexure may comprise an integrally connected extension from the load beam, or may comprise a separate element attached to the load beam. The flexure normally is welded to the load beam at one end, and the other end is a free end at which the head slider is mounted with the slider trailing edge away from the welds.
Typically, the load beam provides a load gimbal in the loading region adjacent the free end of the flexure, and the flexure has a gimbal surface facing the load gimbal. The head slider is mounted on the flexure at a head slider mounting surface opposite the gimbal surface. The flexure is typically a cantilever which is resilient in that it may tilt or twist with respect to the load beam, and the load gimbal and gimbal surface provide a pivot point about which the flexure and mounted head slider are permitted to pitch and roll so that the air bearing surface of the head slider may follow disk surface fluctuations. The gimbal often comprises a dimple in either the load gimbal or the gimbal surface which provides a point of contact with the other of the gimbal surface or the load gimbal. Alternatives comprise connecting bridges or supports which define axes of pitch and roll movements about the pivot point.
To prevent excessive movement of the head slider, shock limiters have been developed which limit the range of movement of the flexure. An example is shown in U.S. Pat. No. 5,771,136, Girard, issued Jun. 23, 1998. Girard shows two "L" shaped shock limiters on the load beam at the edge of the free end of the flexure to prevent excessive movement of the flexure, both shock limiters facing in the same direction. Alternatively, Girard shows a dual cantilever flexure with two "L" shaped shock limiters at one of the cantilevers and a "U" shaped shock limiter extending over the edge of the free end of the second cantilever, all to prevent excessive movement of the flexure. In another example, JP 778436, application JP 05224631, Ikeda et al., filed Sep. 9, 1993, shows two "L" shaped shock limiters at the front and back of a flexure, both facing the same direction. However, the shock limiters of both Girard and Ikeda et al. are open in several directions. In still another example, JP 10255423, application JP09360003, Miller, filed Dec. 12, 1997, shows shock limiter on a load beam. Limit elements at either side of the load beam cooperate with tabs on outer side arms which attach the flexure to the load beam. The tabs are perpendicular to the longitudinal direction and the limit elements may protect against excessive movement of the entire flexure and side arms.
As magnetic disk drives become miniaturized to a greater extent, the suspensions become increasingly delicate and less rigid in all directions. Further, it has become desirable to unload the head sliders from the disks when the disk drive is stopped. The unload is typically by means of a ramp which lifts the suspension away from the disk a slight amount as the actuator moves the suspension radially off the edge of the disk. As the disk drive is restarted, and the spindle motor rotates the disk up to speed, the actuator moves the suspension along the ramp toward the disk, engaging the head slider with the disk to form the air bearing.
The typical head slider is a "negative pressure" slider in which both a positive pressure air bearing and a negative pressure are generated between the head slider and the rotating disk. The pressures cause the head slider to fly at predetermined clearance from the rotating disk with a controlled pitch angle. The pitch angle allows the trailing edge of the slider, at which the head is located, to be held closest to the disk. The slider is thus constrained in pitch angle and fly height by the air bearing and negative pressure.
When the head slider is unloaded from the disk, the negative pressure constraining the head slider must be overcome. The negative pressure will generate a force as high as 3-4 grams, tending to separate the flexure from the gimbal and pitching the trailing edge down. This large negative pressure requires a long traveling distance for disengaging the slider and disk during the unloading process. Damage to the limiter and limiter disengagement are also possible under excessive negative pressure.
At the unloaded position, the suspensions are parked on the corresponding ramps. During a shock event, the head slider tends to pitch down, away from the welded load beam/flexure mount, and two head sliders on opposite sides of a disk may possibly collide with each other, causing permanent damage. Thus, in the prior art, a ramp shelf may be built into the ramp to prevent the pitch motion of the head slider and prevent slider collision. However, if there is limiter disengagement and the load beam jumps away from the ramp under high shock, the flexure may be permanently damaged.